Production of guanidine sulfate



Patented Sept. 11 1951 PRODUCTION OF GUANIDINE SULFATE Nat H. Marsh, Noroton Heights, Conn., assignor to American Cyanamid Company, New York, N. Y., a corporation of Maine No Drawing. Application March 15, 1949, Serial No. 81,625

6 Claims.

1 The present invention relates to the production of guanidine values, and more particularly to a new method whereby such values may be provided in the form of guanidine sulfates.

An object of the present invention is to pro-- While the exact course of the reaction is unknown it is believed that the above equations summarize the overall results. Quite possible, intermediate products are formed and react further to give the final materials.

Diammonium imidodisulfonate may be prepar ed from inexpensive ammonium and sulfur trioxide at atmospheric pressure by methods disclosed in German Patent 562,738. According to that patent, diammonium imidodisulfonate is formed when ammonia and sulfur trioxide are reacted in stoichiometrical quantities according to the equation I but if a large excess of ammonia is used, the triammonium salt is formed as follows;

The triammonium salt is also formed as an intermediate in Equation 1 above, and, while it is not a preferred procedure owing to the additional work involved, it has been found that the triammonium salt may be recovered and heated 2 in a closed pressure-resistant zone to yield guanidine sulfate, and in this respect is a full equivalent of diammonium imidodisulfonate plus ammonia.

In general, the reaction of the present invention is carried out by simply fusing the reactants, and thereafter heating to a suitable temperature for a short period of time, to permit the reaction to occur. Thereafter, the reaction mixture is cooled, extracted with water to obtain an aqueous solution of guanidine sulfate, from which the same or the free guanidine or the other guanidine salts may be isolated by conventional procedures, detailed more fully hereinafter. While the reaction is most conveniently carried out by fusion of the reactants, the use of suitable solvents and/or diluents is permissible.

While the reaction may be carried out over a wide range of temperatures, it is preferred to employ a temperature within the range of substantially 190-300 (3., and preferably, a temperature within the range of substantially 220- 240 C. At temperatures substantially below 190 C., the reaction progresses somewhat slowly, making the use of such temperatures somewhat impractical, whereas at the temperatures substantially above 250 C., decomposition of the desired quantity of guanidine sulfates begins to become appreciable.

The reaction may be conducted in an autoclave, as well as in an open flask, but when the superatmospheric pressures of the autoclave are used,

the reaction time should be reduced.

The following specific examples are set forth below to describe more particularly theprocess of the present invention.

Example 1 A mixture of 36 grams of urea and 63.4 grams of diammoniumimidodisulfonate were placed in an'open beaker equipped with stirrer, and the beaker was heated in an oil bath at a temperature of 220 C. for 2 hours. The reaction mixture was then cooled, ground and leached with water to obtain a 44% yield of guanidine sulfate.

Example 2 Under the same conditions obtaining in Example 1, 24 grams of urea were heated with 84.5 grams of diammoniumimidodisulfonate, and the yield of guanidine sulfate was 49%.

Example 3 Under the same conditions obtaining m the previous examples, 3.6 grams of urea was heated with 25.4 grams of diammoniumimidosulfonate, the yield of guanidine sulfate being 28.5%.

Example 4 Under conditions similar to those of Example 4, 24 grams of urea was heated with 84.5 of diammoniumimidodisulfonate in an autoclave with 6.8 grams of ammonia to obtain a 71.1% yield of guanidine sulfate.

Example 6 Under conditions similar to those obtaining in Examples 4 and 5, 12 grams of urea was heated with 84.5 grams of diammoniumimidodisulfonate and 6.8 grams of ammonia to give a yield of 76.3%

- guanidine sulfate.

In Examples 4, 5, and 6, some of the ammonia and diammoniumimidodisulfonate combined to form triammoniumimidodisulfonate, which in turn reacted with some of the urea to form guanidine sulfate.

The low yield of Example 3 is probably accounted for by the difiiculty in stirring the mixture.

While it will be noted that the yield of guanidine sulfate in the examples using an autoclave increases with increasing diammoniumimidodisulfonate: urea ratio, it is probably uneconomical to increase the amount of diammoniumimidodix sulfonate beyond the mole ratio of 1:1. Thus, generally speaking, a mole ratio of diammoniumimidodisulfonate to urea of 1:1 is preferred. Actually, any conceivable ratio of these two reactants will result in the formation of some guanidine sulfate if heated together within the temperature range 190-300 C.

The guanidine sulfate usually provided by the process of the present invention is predominantly in the form *of the diguanidine sulfate. Obviously, the more acidic monoguanidine sulfate may be readily prepared therefrom by acidifying an aqueous solution of the diguanidine sulfate with sulphuric acid. In general, at a pH of about 2, the salt is predominantly in the form of the monoguanidine sulfate, whereas at a pH of about 7 the sulfate is predominantly in the form of the diguanidine sulfate.

The isolation of the guanidine sulfate may be effected by any of the conventional means, such as by cooling or evaporating an aqueous solution to cause crystallization, or by adding a watermiscible organic liquid, such as ethanol, to decrease the solubility of the salt and cause its precipitation. Because of the appreciable solubility of the sulfate, the latter technique is usually resorted to, despite the cost of the alcohol. The guanidine molecule being that desired, said guanidine values can also be isolated by forming a less soluble salt, such as a picrate, a carbonate, nitrate, or a phosphate. The preparation of such less soluble salts is effected by simply adding an equivalent amount of the corresponding ammonium or metal salt of the acid to the aqueous solution of the sulfate, and inducing crystallization by any conventional means, such as those aforementioned.

The guanidine sulfates provided by the process of the present invention, are valuable chemicals, being useful as fireproofing agents, in the preparation of resins and blueprint materials, and as intermediates in the preparation of chemotherapeutic agents, pharmaceuticals, surface-active agents, explosives, and the like.

While the invention has been described with particular reference to specific embodiments, it is to be understood that it is not to be limited thereto, but is to be construed broadly and restricted solely by the scope of the appended claims.

I claim:

1. The process of preparing a guanidine sulfate comprising reacting urea with a member of the group consisting of diammonium imidodisulfonate and triammonium imidodisulfonate at a temperature within the range of substantially -300 C.

2. The process of preparing a guanidine sulfate comprising reacting urea with a member of the group consisting of diammonium imidodisulfonate and triammonium imidodisulfonate at a temperature within the range of substantially 220-240 C.

3. The process of claim 2 in which the reaction is carried out for a time ranging from about /2 hour to about 5 hours.

4. The process of preparing a guanidine sulfate comprising reacting urea with a member of the group consisting of diammonium imidodisulfonate and triammonium imido's'ulfonate within the range of substantially 190-300 C. in a ratio of substantially one mole of urea to substantially to 2 moles of disulfonate.

5. The process of preparing a guanidine sulfate comprising reacting urea with diammonium imidodisulfonate at a temperature of approximately 220 C., and recovering the thus-formed guanidine sulfate.

6. The process comprising reacting urea with triammonium imidodisulfonate under superatmospheric pressure, whereby a guanidine sulfate is formed, and recovering the thus-formed uanidine sulfate.

NAT H. MARSH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,212,152 Cupery Aug. 20, 1940 2,464,247 Mackay Mar. 15, 1949 FOREIGN PATENTS Number Country Date 611,417 Great Britain Oct. 29, 1948 OTHER REFERENCES Franklin: Nitrogen System of Compounds (1935), pp. 167 to 169. 

1. THE PROCESS OF PREPARING A GUANIDINE SULFATE COMPRISING REACTING UREA WITH A MEMBER OF THE GROUP CONSISTING OF DIAMMONIUM IMIDODISULFONATE AND TRIAMMONIUM IMIDODISULFONATE AT A TEMPERATURE WITHIN THE RANGE OF SUBSTANTIALLY 190*-300* C. 